Here's the verdict of the Lean spike for now
Here's the verdict of the Lean spike for now Well took the car to the dyno today. We finally got to check my Fuel pressure under load with N20. Well the car dynoed 347RWHP @5600 and 352RWTQ N/A. Then dynoed on the N20 to a 415RWHP @5300RPM and 456RWTQ. As for the spike yes it still does a slight lean spike. The bottle PSI was about 950PSI. We purged it really well before hand. The lean spike went to 13.4:1 at the leanest point of 3600RPM with the N20 turning on at 3400RPM. I had a dip in HP of about 10RWHP instead of the 40RWHP loss before. The fuel curve stayed at about 11:1 for the most part of the RPM range. The fuel pressure stays at 55PSI on the bottle. It drops to about 56PSI N/A. Well heres the part that bothers me the most. When the Fuel noid opens intially the Fuel pressure gauge shows a spike that is a blink of an eye quick. It drops drastically when it initially opens to dunno what like 30PSI right when it hits. If I would've blinked i would've never seen this. The more I thought about it this has to be normal. We have a nonreturn fuel system. There for the slightest change of fuel needed is going to momentarily do this. What I'm concerned about is if it drops to 55psi now how much more will it drop with the 100HP jets in?? Please confirm the spike is normal!!!! There is no way its a lack of fuel pump. It couldn't matter what pump i have on the car its still going to be regulated at the same PSI. There's no way to get rid of that spike I see. If this is not true someone please do tell with detail though. Thanks again to all those that have replied to the previous post. If this does spike lean to 13.4:1 now how much more lean do you think it'll spike with the 100 jet? thanks again
*Bad Trader*
Joined: Nov 2001
Posts: 1,459
Likes: 0
From: here and there
Re: Here's the verdict of the Lean spike for now i think you hit the nail on the head, how ever i dont think the fuel jet will affect you much if at any, the surge of fuel is filling the lines and backing up at the jet, your regulator can catch up by that point..
TECH Resident
Joined: Mar 2002
Posts: 770
Likes: 0
From: WA
Re: Here's the verdict of the Lean spike for now What did you do different? Your A/F ratio's are alot better. Yes the spike is normal.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> Well heres the part that bothers me the most. When the Fuel noid opens intially the Fuel pressure gauge shows a spike that is a blink of an eye quick. It drops drastically when it initially opens to dunno what like 30PSI right when it hits. If I would've blinked i would've never seen this. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">This is why I don't like fuel pressure safty switches. The pressure shoots down to 30. the switch shuts off. Then the fuel pressure jumps back up and the switch turns on again. It's possible for the switch to stutter on,off, on,off, on,off.
Anyway. A fuel pump could still help you. Yes it is true. Even with a fuel pump, the car its still going to be regulated at the same PSI. BUT, with more pressure behind the regulator. The PSI will get up to the regulated pressure faster. For your blink of the eye fuel drop. It will make the fuel drop off less, and regain max pressure faster.
I don't think your lean spike is a problem. It's alot better now.
The speed shop has some cool nitrous gages, and some handy A/F charts too.
http://www.speedshop.org/detail.asp?...T_ID=NEDT-0011
Good luck
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> Well heres the part that bothers me the most. When the Fuel noid opens intially the Fuel pressure gauge shows a spike that is a blink of an eye quick. It drops drastically when it initially opens to dunno what like 30PSI right when it hits. If I would've blinked i would've never seen this. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">This is why I don't like fuel pressure safty switches. The pressure shoots down to 30. the switch shuts off. Then the fuel pressure jumps back up and the switch turns on again. It's possible for the switch to stutter on,off, on,off, on,off.
Anyway. A fuel pump could still help you. Yes it is true. Even with a fuel pump, the car its still going to be regulated at the same PSI. BUT, with more pressure behind the regulator. The PSI will get up to the regulated pressure faster. For your blink of the eye fuel drop. It will make the fuel drop off less, and regain max pressure faster.
I don't think your lean spike is a problem. It's alot better now.
The speed shop has some cool nitrous gages, and some handy A/F charts too.
http://www.speedshop.org/detail.asp?...T_ID=NEDT-0011
Good luck
TECH Enthusiast
Joined: Nov 2001
Posts: 617
Likes: 0
From: Milford, Ohio
Re: Here's the verdict of the Lean spike for now Another thought is you're going to be in the fuel system anyway would be to move the regulator and return line closer to the motor, thus less slack volume to compensate for.
Re: Here's the verdict of the Lean spike for now Zturd, I just found my dyno graph's of my 100 shot runs and guess what, I have that same lean spike going up to 14.6 at 3600 RPM, the actual graph didn't indicate that but the data sheet did. So I think your good to go up to the 100 shot. Your 11.1 Af looks much better and you should be good for a really low 11 sec run, I got a 11.22 @ 128 with some wheel spin. I to had issues with that POS FPSS and it's now gone. The Walbro is definately a good idea just to be on the safe side when you move up to the 150 shot, yes, you will do it <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> ...Report back after some track runs and good luck to you.
Dan
Dan
